6,006 research outputs found
New Physics Signals through CP Violation in B -> rho,pi
We describe here a method for detecting physics beyond the standard model via
CP violation in B->rho,pi decays. Using a Dalitz-plot analysis to obtain alpha,
along with an analytical extraction of the various tree (T) and penguin (P)
amplitudes, we obtain a criterion for the absence of new physics (NP). This
criterion involves the comparison of the measured |P/T| ratio with its value as
predicted by QCD factorization. We show that the detection of NP via this
method has a good efficiency when compared with the corresponding technique
using B->pi,pi decays.Comment: 8 pages, 4 figures, talk given at MRST 2004: From Quarks to
Cosmology, Concordia University, Montreal, May 200
Exploring CP Violation with B_d -> D K_s Decays
We (re)examine CP violation in the decays B_d -> D K_s, where D represents
D^0, D(bar), or one of their excited states. The quantity can be extracted from the time-dependent rates for and , where the decays to
. If one considers a non-CP-eigenstate hadronic final state to
which both D(bar) and D^0 can decay (e.g. ), then one can obtain two
of the angles of the unitarity triangle from measurements of the time-dependent
rates for and .
There are no penguin contributions to these decays, so all measurements are
theoretically clean.Comment: 15 pages, LaTeX, no figure
B-Decay CP Asymmetries, Discrete Ambiguities and New Physics
The first measurements of CP violation in the system will likely probe
, and . Assuming that the CP angles
, and are the interior angles of the unitarity
triangle, these measurements determine the angle set
except for a twofold discrete ambiguity. If one allows for the possibility of
new physics, the presence of this discrete ambiguity can make its discovery
difficult: if only one of the two candidate solutions is consistent with
constraints from other measurements in the and systems, one is not sure
whether new physics is present or not. We review the methods used to resolve
the discrete ambiguity and show that, even in the presence of new physics, they
can usually be used to uncover this new physics. There are some exceptions,
which we describe in detail. We systematically scan the parameter space and
present examples of values of and the new-physics
parameters which correspond to all possibilities. Finally, we show that if one
relaxes the assumption that the bag parameters \BBd and \BK are positive,
one can no longer definitively establish the presence of new physics.Comment: 29 pages, LaTeX, 1 figures, presentation substantially reworked,
physics conclusions unchanged. This version will be published in Phys. Rev.
The Higher Order Schwarzian Derivative: Its Applications for Chaotic Behavior and New Invariant Sufficient Condition of Chaos
The Schwarzian derivative of a function f(x) which is defined in the interval
(a, b) having higher order derivatives is given by
Sf(x)=(f''(x)/f'(x))'-1/2(f''(x)/f'(x))^2 . A sufficient condition for a
function to behave chaotically is that its Schwarzian derivative is negative.
In this paper, we try to find a sufficient condition for a non-linear dynamical
system to behave chaotically. The solution function of this system is a higher
degree polynomial. We define n-th Schwarzian derivative to examine its general
properties. Our analysis shows that the sufficient condition for chaotic
behavior of higher order polynomial is provided if its highest order three
terms satisfy an inequality which is invariant under the degree of the
polynomial and the condition is represented by Hankel determinant of order 2.
Also the n-th order polynomial can be considered to be the partial sum of real
variable analytic function. Let this analytic function be the solution of
non-linear differential equation, then the sufficient condition for the
chaotical behavior of this function is the Hankel determinant of order 2
negative, where the elements of this determinant are the coefficient of the
terms of n, n-1, n-2 in Taylor expansion.Comment: 8 page
Can One Measure the Weak Phase of a Penguin Diagram?
The b -> d penguin amplitude receives contributions from internal u, c and
t-quarks. We show that it is impossible to measure the weak phase of any of
these penguin contributions without theoretical input. However, it is possible
to obtain the weak phase if one makes a single assumption involving the
hadronic parameters. With such an assumption, one can test for the presence of
new physics in the b -> d flavour-changing neutral current by comparing the
weak phase of B_d^0-{\bar B}_d^0 mixing with that of the t-quark contribution
to the b -> d penguin.Comment: 20 pages, no figure
CP Violation in Three-Body Chargino Decays
CP violation in supersymmetry can give rise to rate asymmetries in the decays
of supersymmetric particles. In this work we compute the rate asymmetries for
the three-body chargino decays \tilde\chi^\pm_2 \to \tilde\chi^\pm_1 HH,
\tilde\chi^\pm_2 \to \tilde\chi^\pm_1 ZZ, \tilde\chi^\pm_2 \to \tilde\chi^\pm_1
W^+ W^- and \tilde\chi^\pm_2 \to tilde\chi^\pm_1 ZH. Each of the decays
contains contributions mediated by neutral Higgs bosons that can possibly go on
shell. Such contributions receive a resonant enhancement; furthermore, the
strong phases required for the CP asymmetries come from the widths of the
exchanged Higgs bosons. Our results indicate that the rate asymmetries can be
relatively large in some cases, while still respecting a number of important
low-energy bounds such as those coming from B meson observables and electric
dipole moments. For the parameters that we consider, rate asymmetries of order
10% are possible in some cases.Comment: 17 pages, 4 figures, published versio
CP Asymmetry in B_d --> phi K_S: Standard Model Pollution
The difference in the time dependent CP asymmetries between the modes and is a clean signal for physics beyond the Standard
Model. This interpretation could fail if there is a large enhancement of the
matrix element of the operator between the initial state
and the final state. We argue against this possibility and propose
some experimental tests that could shed light on the situation.Comment: 9 pages, Revte
Recommended from our members
Subregional Hippocampal Thickness Abnormalities in Older Adults with a History of Heavy Cannabis Use.
Background and Aims: Legalization of cannabis (CB) for both medicinal and, in some states, recreational use, has given rise to increasing usage rates across the country. Of particular concern are indications that frequent CB use may be selectively harmful to the developing adolescent brain compared with adult-onset usage. However, the long-term effects of heavy, adolescent CB use on brain structure and cognitive performance in late-life remain unknown. A critical brain region is the hippocampus (HC), where there is a striking intersection between high concentrations of cannabinoid 1 (CB1) receptors and age-related pathology. Design: We investigated whether older adults (average age=66.6+7.2 years old) with a history of early life CB use show morphological differences in hippocampal subregions compared with older, nonusers. Methods: We performed high-resolution magnetic resonance imaging combined with computational techniques to assess cortical thickness of the medial temporal lobe, neuropsychological testing, and extensive drug use histories on 50 subjects (24 formerly heavy cannabis users [CB+ group] abstinent for an average of 28.7 years, 26 nonusers [CB- group]). We investigated group differences in hippocampal subregions, controlling for age, sex, and intelligence (as measured by the Wechsler Test of Adult Reading), years of education, and cigarette use. Results: The CB+ subjects exhibited thinner cortices in subfields cornu ammonis 1 [CA1; F(1,42)=9.96, p=0.0003], and CA2, 3, and the dentate gyrus [CA23DG; F(1,42)=23.17, p<0.0001], and in the entire HC averaged over all subregions [F(1,42)=8.49, p=0.006]. Conclusions: Negative effects of chronic adolescent CB use on hippocampal structure are maintained well into late life. Because hippocampal cortical loss underlies and exacerbates age-related cognitive decline, these findings have profound implications for aging adults with a history of early life usage. Clinical Trial Registration: ClinicalTrials.gov # NCT01874886
Determining the Quark Mixing Matrix From CP-Violating Asymmetries
If the Standard Model explanation of CP violation is correct, then
measurements of CP-violating asymmetries in meson decays can in principle
determine the entire quark mixing matrix.Comment: 8 pages (plain TeX), 1 figure (postscript file appended), DAPNIA/SPP
94-06, NSF-PT-94-2, UdeM-LPN-TH-94-18
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